Question

вычислите рациональным способом :
1) 30*2,9-2,9*28+28*2,7-2,7*26+26*2,5-2,5*24+24*2,3-2,3*22

Answer 1

30*2,9-2,9*28+28*2,7-2,7*26+26*2,5-2,5*24+24*2,3-2,3*22=
2.9(30-28)+ 2.7(28-26)+2.5(26-24)+2.3(24-22)=
2.9*2+ 2.7*2+2.5*2+2.3*2=
2*(2.9+ 2.7+2.5+2.3)=
2*10.4= 20.8